I don't know how to tell my mum that I'm engaged to be married to my same-sex partner. For most families this would be a joyous occasion that deserves celebration. For my mum, however, it will be seen as a situation, one that needs to be handled and kept out of sight.

My fiance's name has been mentioned many times, but it's only these last six months that his status as a partner has been made known to her, and she has yet to meet him (or show any desire to). He is a lovely, kind man. He's keen to meet her and in other circumstances my mum would probably like him. Given how coldly she treated my brother's girlfriend on meeting her because she was deemed past (grand)child-bearing age, though, my mum discovering her other son's partner has a penis is likely to be Arctic in comparison.

My mother has never really dealt with or spoken about my sexuality. She discovered gay pornography in my room in my late teens and I was dragged out of the closet when neither my mum nor I were ready. I returned home one day broken-hearted after a relationship ended, and my mum saw the grief that anyone, regardless of sexuality, would feel over lost love, and thawed somewhat as she skirted around my tears. Since then, however, my sexuality has not been discussed.

I think of telling her that I'm engaged and then dread the look on her face. A phonecall seems too casual, and a letter seems preferable but wrong. It is the fallout that I am struggling to confront, and the thought that I may gain a husband but lose my mother.

C, via email

Your longer letter was funny, warm, observant. I couldn't help thinking that if your mother could read it, how could she fail to be incredibly proud of you, even if she is – obviously – having great difficulty accepting your sexuality?

I think, deep down, your mother might be desperate to reach out to you but it seems convention is shackling her to her prejudices.

You told me your father was dead, so he can't help you in breaking the news. I'm sorry about that. You also said you were worried about how to contain your grandma and wider family finding out.

I contacted the psychotherapist Dominic Davies of Pink Therapy (pinktherapy.com/ukcp.org.uk). He helped me to see that your problem could equally be applied to anyone worried about telling their mother about a partner they're pretty sure she won't like. After all, she doesn't approve of your brother's choice of partner either.

"In a way, we can see this as a perfectly ordinary situation, a developmental task that we all face: leaving adolescence, becoming adults, becoming individuals away from the shadow of our parents. Being gay robs us of the normal developmental processes, because we don't (often) socialise at the same time and rate." He's not saying you're immature by the way (far from it) just that you're having to deal with tasks that heterosexual people face too, just a bit later: in this case the disapproval of a parent over choice of partners.

Davies suggests writing to your mother and telling her your news. His reckoning was that you've had a lot longer to get used to your sexuality than your mother has. My reaction to this was "what happens if she just ignores it" as is her wont? So Davies said to put in the letter that you'll follow it up with a phone call (a week or so hence) and then a visit. "This gives her time to collect herself and start to think it through, so it doesn't feel too confrontational. Do it in a graded way."

If you had an ally in the family, it might be an idea to bring them too – is there someone your mother really listens to? But it's important to not make her feel ganged up on.

I really want to give your mother the benefit of the doubt that she will step up and come to your wedding. What a shame if she misses out on this important day. But, of course, you can't make her behave any particular way. I'd counsel against cutting her out of your life if she chooses not to be there.